<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // var是给window声明变量、、、、let不是

        var age = 20;
        var obj = {
            age: 18,
            say: () => {
                console.log(this.age)
            }
        };
        obj.say()
            // var age = 20; {
            //     age = 18;
            // }

        // console.log(window.age)
    </script>
</body>

</html>